The goal of this project is to evaluate school-based caries prevention programs. To accomplish this we will analyze a six-year longitudinal data set of 9260 children attending Title 1 schools who participated in a school- based caries prevention program. This will allow us to identify and quantify clinical and patient-centered variables that enhance the delivery and effectiveness of caries prevention and predict caries progression in high-risk children. Dental caries is the most common preventable childhood disease. Caries is over five times more common than asthma among children aged 5 to 17, and poor oral health has been associated with respiratory disease, cardiovascular disease, and diabetes. Untreated caries affects 28% of U.S. school-age children (more than 10 million), and almost 50% of minority, underserved, and Medicaid recipients. Guidance from federal and state governments, health foundations, and clinical organizations all recommend school- based caries prevention as an effective means of increasing access to and improving health. Sadly, current data from the Centers for Disease Control and Prevention indicate that only 14% of children receive effective preventive dental services. There are three primary barriers to the dissemination and implementation of school- based caries prevention: (1) while efficacy trials demonstrate success in caries control, there is little evidence of effectiveness in large pragmatic studies; (2) littleis known of the cumulative effects of prevention over time for students of varying age, so optimization is difficult; and (3) previous studies of longitudinal data from prevention programs did not examine student cohorts who most needed care. Our goal in this project is to use secondary data analysis to identify key criteria for optimizing school-based caries prevention programs. In particular, we will quantify: (1) impact on the incidence and prevalence rate of untreated caries across children, teeth, and tooth surfaces; (2) intra-individual change and the causal effects of prevention over time; and (3) predicted probabilities of decay development to optimize care, focusing on delivery time, targeted care for high- risk groups, and clinically relevant prevention methods. We will use novel statistical methods to properly account for the complex research design, control for relevant observed and unmeasured confounders, and utilize all available data to ensure adequate statistical power. This research is significant in tht it will be the first to systematically analyze comprehensive caries prevention in a longitudinal dataset of students attending Title 1 schools. The outcomes have the potential to provide foundational information for national implementation of effective school-based caries prevention programs.